AudioLink is a system that analyzes and processes in-world audio into many different highly reactive data streams and exposes the data to VRChat Udon, world shaders, and avatar shaders.
The per-frequency audio amplitude data is first read briefly into Udon using Unity's GetOutputData. It is then sent to the GPU for signal processing and buffered into a CustomRenderTexture. Then, the CustomRenderTexture is broadcast globally (called _AudioTexture) which can be picked up by shaders both in-world and across all avatars.